Human cystic hydatidosis in Italy: a public health emergency? Past to present

Starting from 1991 the Central Office of Statistics ISTAT, according to changed regulations on notification of infective diseases, stopped reporting official national data on human hydatidosis. On the other hand until then notified data, concerning only about a hundred cases per year in mean during the last decades and just 36 in 1991, appeared unreliable, suggesting a diffusion far from the actual. Owing to specific studies on different research groups it is possible to try to describe a not exhaustive but indicative pattern of trend of human hydatidosis in Italy. More recent publications regarding different regions report an annual mean incidence rate of surgical cases of 9.77/100,000 inhabitants in Sardinia, of 1.57 in Emilia Romagna, of 2.30 in Sicily and of 2.33 in Apulia, the latter encompassing only hepatic cysts treated in the region, irrespective of residence of subjects. A comparison with previous studies regarding the period between 1948-1952 and 1980-84 respectively, indicates an increase in the more recent surveys. However, as even underlined by Authors, former surveys were not all-embracing (for example not including patients from private Clinics etc). On the other hand during time, improvements in surgical as well in anaesthesiological skills have made surgery possible in patients previously inoperable, and particularly in old subjects. Conversely, at present, availability of alternative therapies such as chemotherapy, PAIR or modified PAIR-based techniques may allow cases to avoide surgical surveys. However, actual parasite burden in humans may be estimated by assessing the trend of likely young cysts, as due to recent infections. Rate of pulmonary cysts, that are sure to be young, was of 48.6%/100,000 inhab. in 1952 in Italy, then falling to 18.2 in 1980-84 in the 9 considered regions, to 12.7 in Sicily (1989-91), 6.5 in Emilia-Romagna (1989-93) and 15.7 in Sardinia (1990-95). Another "class" of surely young cysts regards all cysts in young age group that necessarily have been recently infected. Ratio of infection rates in the old/young people was around 1 in 1941-52 but was exceeding 3 in 1980-84. In addition available data from more recent surveys indicate that ratio is at present still relatively low in Sardinia (3.9), where sheep-breeding is widespread, and dog-livestock-man interaction is most likely to exist, and conversely is very high in Emilia-Romagna (5.75) where pastoral economy is not prevalent (just 92,000 sheep). Actual trend both parasitological and in terms of public health would ameliorate if studies were provided with long temporary series. In Sardinia all hydatid cases surgically treated from 1969 to 1995 have been registered and analysed with a standardized methodology. During the considered period incidence appears nearly unvaried (16.9 in 1969 vs 15.8 in 1985), with a fall only for the last 5 years (9.1 in 1995), and with an increase regarding 1984-88 period. Analysis according to cyst localization strongly suggests that fall in the last period is only weakly related to hepatic cysts, that conversely are near completely responsible of rise in 1984-88. On the contrary for pulmonary cysts, i.e. young cysts, a slow but continuous and significant decrease (from 6.5 in 1969 to 1.4 in 1995) is evident. In the same way the above- mentioned old/young ratio rises from 1.7 (1969-79) to 3.9 (1990-95). On the whole analysed data suggest that although parasitic burden, strong in central-south Italy for decades, is now slow lowering due to structural changes and improvements in general conditions of life rather to specific preventive actions, human hydatidosis still represents a public health problem that will continue in the future as, because of latency, incidence rates will stay long relevant.     

Human hydatidosis in Sardinia. Epidemiologic study of the cases operated on from 1974 to 1981

A retrospective survey of surgical cases to obtain baseline data on hydatid disease in Sardinia from 1974 to 1981 revealed an annual mean rate of 11.1/100.000 population. However, real prevalence is obviously higher, since infection is not always synonymous with disease and surgical incidence should be regarded as the figure that counts. Information on sex, age, residence, occupation, cyst location, number of re-operations was collected to assess the public health impact to hydatidosis within the island. The obtained results indicate that not all population is at equal risk, being hydatid disease most prevalent in rural areas and particularly in the districts where sheep-breeding is highly diffused (annual mean rate greater than 20/100.000 population). The highest rate was observed in farmers and shepherds (34.2/100.000) respect to retired (14.1/100.000), housewives (10.9/100.000), employed in services (8.9/100.000) and students (8.3/100.000). Over 55% of the cysts were found in the liver, about 30% in the lung and 15% in other sites. A correlation between age and cyst location and between profession and cyst location was shown. Pulmonary cysts were prevalent in children and young people, hepatic in grown-up people, whereas nearly the same hepatic and pulmonary frequency was observed in shepherds. Comparisons between previous surveyed periods were done and results were discussed, suggesting the need of a continuous and well-planned control programme.     

Intrafollicular steroids and anti-mullerian hormone during normal and cystic ovarian follicular development in the cow

Development of follicular cysts is a frequent ovarian dysfunction in cattle. Functional changes that precede cyst formation are unknown, but a role for anti-Müllerian hormone (AMH) in the development of follicular cysts has been suggested in humans. This study aimed to characterize intrafollicular steroids and AMH during follicular growth in a strain of beef cows exhibiting a high incidence of occurrence of follicular cysts. Normal follicular growth and cyst development were assessed by ovarian ultrasonography scanning during the 8 days before slaughtering. Experimental regression of cysts was followed by rapid growth of follicles that reached the size of cysts within 3-5 days. These young cysts exhibited higher intrafollicular concentrations of testosterone, estradiol-17beta, and progesterone than large early dominant follicles did in normal ovaries, but they exhibited similar concentrations of AMH. Later-stage cysts were characterized by hypertrophy of theca interna cells, high intrafollicular progesterone concentration, and high steroidogenic acute regulatory protein mRNA expression in granulosa cells. Progesterone and AMH concentrations in the largest follicles (> or =10 mm) and cysts were negatively correlated (r = -0.45, P < 0.01). Smaller follicles (<10 mm) exhibited higher intrafollicular testosterone and estradiol-17beta concentrations in ovaries with cysts compared to normal ovaries. During follicular growth, AMH concentration dropped in follicles larger than 5 mm in diameter and in a similar way in ovaries with and without cysts. In conclusion, enhanced growth and steroidogenesis in antral follicles <10 mm preceded cyst formation in cow ovaries. Intrafollicular AMH was not a marker of cystic development in the cow, but low AMH concentrations in cysts were associated with luteinization.     

Further studies on prevalence of hydatidosis in slaughtered animals from North Jordan

Examination of 471 sheep, 118 goats, 157 cattle and 56 camels slaughtered in abattoirs in North Jordan was carried out during March-May 1984. Drought conditions that prevailed during the preceding winter led to slaughtering old female sheep (greater than or equal to 4 years) due to scarcity of food, which allowed us to analyse the prevalence of hydatidosis in various age groups of sheep. An overall infection rate of 27.8, 1.7, 5.8 and 10.7 percent was found in sheep, goats, cattle and camels, respectively. The infection rate was as low as 1.5 percent in male and 1.9 percent in female sheep under 2 years of age. However, the rate of hydatid infection increased with age and reached as high as 63.7 percent in ewes 4 years of age and older. The percentage of animals with fertile cysts was also highest in sheep (68.7 percent of infected animals) and increased with age reaching 100 percent in ewes which were 10 years of age or older. Analysis of all cysts recovered from the livers and lungs of infected ewes from various age groups revealed a sharp increase in the mean total number of cysts in age groups over 8 years of age. The fertility rate of the cysts in the liver was significantly greater in ewes 6 years old or more (64.8--78.6 percent) than in younger age groups (8.7-46.2 percent). In the lung, the fertility rate increased progressively with age reaching as high as 97.9 percent in ewes 10 years old or more. These findings of high infection and fertility rates of hydatid disease in sheep, particularly of older age groups, prompt plans for further epidemiological studies and control programmes.     

Epidemiology of hydatidosis in the province of Sassari, Italy

Cystic echinococcosis is endemic in certain parts of the world, including Sardinia, Italy. It was performed a study in the province of Sassari in order to evaluate the incidence of the infection in man and the effects of control programs since 1964 to 2002. Data obtained by surgical records, hospital discharge forms, radiological and pathological files were collected using a case report form. During the years 1964-2002, 2702 new cases were identified (average annual incidence: 17 per 100,000) and 1981 (73.3%) were submitted to surgical treatment. In 57.3% municipalities no cases were observed during the years 1998-2002. Males are more affected (56.2%), mostly farmers-shepherdess (68.6 per 100,000) and pensioners (59.6 per 100,000). Control measures led to a significant decline in the incidence rate of hydatidosis during the period 1964-2002, dropping by 27.6 per 100,000. The mean age of surgical patients increased during the years of surveillance, such as the surgical liver/lung ratio as a consequence of a cohort effect. The durability of control programs is the corner stone for obtaining a significant decrease of this infection.     

Formation of ovarian follicular cysts and corpora lutea after treatment with antihistamine or indomethacin in prepubertal gilts

Roles of histamine and prostaglandins in the induction of ovarian cysts after unilateral ovarian manipulation (MAN) and in the process of ovulation were evaluated in prepubertal gilts treated with pregnant mare's serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG). Administration of pyrilamine maleate, an H1 receptor antagonist, before MAN or hCG injection reduced the number of cysts formed but did not alter ovulation rate. Administration of cimetidine, an H2 receptor antagonist, failed to alter the incidence, number, or diameters of cysts formed in response to MAN or the ovulation rate on non-MAN ovaries. Administration of indomethacin, an inhibitor of prostaglandin synthesis, before MAN or hCG injection did not alter the incidence, number, or diameters of cysts formed on MAN ovaries but reduced the number of corpora lutea on non-MAN ovaries. Excessive accumulation of fluid in ovarian cysts apparently was mediated by histamine interacting with the H1-type receptor. Enhanced secretion of prostaglandins produced by the cyclooxygenase pathway did not contribute to development of ovarian cysts but, unlike histamine, was required for formation of corpora lutea in prepubertal gilts treated with PMSG and hCG.     

腹泻患儿粪便A群轮状病毒抗原检测的结果分析

目的：了解本地区腹泻婴幼儿的A群轮状病毒感染情况及其流行特点。方法：采用胶体金法对我院2009年10月-2010年9月2104例有腹泻和肠炎特征的婴幼儿粪便进行A群轮状病毒抗原检测。结果：在2104例受检者中,A群轮状病毒感染的总阳性率是24．71％,其中男性感染率24．17％,女性为25．40％。不同年龄组间以1—2岁婴幼儿感染率最高,为32．13％,0-1岁为20．72％,2-5岁为12．03％。感染的季节特征是秋末冬初季（10—12月）阳性率最高,为42．82％,春末夏初季（4．6月）最低,为8．81％。结论：由A群轮状病毒感染引发的急性腹泻主要发生在1-2岁的婴幼儿,各个季节均有发生,以秋末冬初季为高发。     

Aging and the immune response. I. Antibody formation and chronic infection in Toxoplasma gondii-infected mice

Studies were performed to determine the effect of aging on the antibody response and cyst formations after infection with a relatively avirulent strain of the intracellular parasite Toxoplasma gondii. When compared with young mice (4 months), aged mice showed a significant decrease in the magnitude of humoral immune response to infection. This decrease was observed at the peak of the acute infection and also during chronic infection. Evaluation of the presence of Toxoplasma cysts, a measure of the latent infection, revealed that the numbers of tissue cysts present 11 weeks after infection increased with the age of the mice at time of infection. The larger numbers of cysts in older mice which had received the same inoculum size of T. gondii as young mice, together with our previous observations of increased susceptibility of these older mice to T. gondii, suggest that an age-related decrease in the early immune response to this infection allows an increased multiplication of the organism in vivo, leading to increased cyst numbers or death.     

Giardia muris: Correlation between oral dosage,course of infection,and trophozoite distribution in the mouse small intestine

Oral inoculations of Giardia muris cysts to CD-1 Swiss mice resulted in a reproducible pattern of infection measured by cyst excretion and the number of trophozoites in the small intestine. Housing of animals together or individually did not alter the pattern of cyst release for the first 30 days of infection. Administration of 10 to 10⁵ cysts/mouse resulted in a similar rate of cyst excretion from Day 10 to the end of the infection period. There was a direct correlation between the size of inoculum and the length of the latent period. Mice which received larger doses (10³, 10⁴, 10⁵) had significantly higher numbers of cysts in feces during the first week of infection, compared to those which received lower doses (10 or 100). The extent of trophozoite colonization and their distribution in the small intestine was not related to the size of inoculum. The location of trophozoites in the small intestine varied during the infection. In the first 3 to 8 days of infection the trophozoites were situated in the upper 25% of the small intestine, but moved posteriorly (upper 40%) during the period of peak cyst output. The number of trophozoites in the small intestine and cyst excretion were found to be proportional at all stages of infection.     

Prevalence and incidence of Helicobacter pylori Infection in a healthy pediatric population in the Lisbon area

Background: Helicobacter pylori is mainly acquired in childhood. Although adult studies reported a high prevalence of H. pylori infection in Portugal, the actual rate in children remains unknown. This study aimed to determine the prevalence and the incidence of H. pylori infection in an asymptomatic pediatric population of the Lisbon area and to correlate prevalence with sociodemographic determinants. Materials and Methods: Helicobacter pylori infection was determined by stool antigen test in 844 asymptomatic children (age 0–15 years; 49.4% boys). For the incidence study, H. pylori‐negative children in the prevalence study were followed‐up every 6 months over a 3‐year period. Results: The global prevalence of H. pylori infection was 31.6%, increasing with age (19.9, 37.0 and 51.5%, in age groups 0–5, 6–10, and 11–15, respectively), but was similar among genders (34.5% in boys and 28.4% in girls). Older age and attendance of nursery/kindergarten during preschool constituted independent risk factors. The overall estimated incidence was 11.6 per 100 child‐years (CY). Although 47.5% of children acquired H. pylori infection before 5 years of age, the mean age of acquisition was 6.3. The incidence of infection was similar among the three age groups (11.5, 13.0, and 10.5 per 100 CY, in age groups 0–5, 6–10, and 11–15, respectively). Conclusions: The prevalence of H. pylori infection in the Portuguese pediatric population is still high. Although this study confirmed that the highest acquisition rate occurs at young age, it showed that in high‐prevalence populations, older children can also acquire H. pylori infection at a rate similar to that of young children.     

Part III – Treatment of Ureterovesical Reflux

Of 134 girls with demonstrable ureterovesical reflux, 61 (105 ureters) had the reflux surgically corrected with an overall surgical cure rate of 97 percent. In the remaining 73 children (112 ureters), the reflux was treated conservatively with medical management alone. During the follow-up period no significant differences were demonstrated in the overall incidence of urinary tract infection; two years following corrective operation or medical treatment more than 50 percent of both medically and surgically treated children were still experiencing infections. A pronounced decrease, however, occurred in the incidence of clinical pyelonephritis among the surgically treated group. Following correction of reflux, the incidence of pyelonephritis was similar in both medically and surgically treated cases and was approximately the same as that found in a comparable group of children without reflux.In approximately two-thirds of refluxing renal units in which there was evidence of clubbing and scarring before medical or surgical therapy, deterioration progressed during the follow-up period. In most of these cases infection control was felt to be inadequate with episodes of clinical pyelonephritis occurring during the period of medical management, or, in the surgically treated group, occurring just before corrective operation and the scar appearing within two years after operation.The majority of renal units in which calyceal clubbing and parenchymal scarring was present had the most severe grades of reflux.     

Tuberculosis in Healthcare Workers and Infection Control Measures at Primary Healthcare Facilities in South Africa

Background

Challenges exist regarding TB infection control and TB in hospital-based healthcare workers in South Africa. However, few studies report on TB in non-hospital based healthcare workers such as primary or community healthcare workers. Our objectives were to investigate the implementation of TB infection control measures at primary healthcare facilities, the smear positive TB incidence rate amongst primary healthcare workers and the association between TB infection control measures and all types of TB in healthcare workers.

Methods

One hundred and thirty three primary healthcare facilities were visited in five provinces of South Africa in 2009. At each facility, a TB infection control audit and facility questionnaire were completed. The number of healthcare workers who had had TB during the past three years was obtained.

Results

The standardised incidence ratio of smear positive TB in primary healthcare workers indicated an incidence rate of more than double that of the general population. In a univariable logistic regression, the infection control audit score was significantly associated with reported cases of TB in healthcare workers (OR=1.04, 95%CI 1.01-1.08, p=0.02) as was the number of staff (OR=3.78, 95%CI 1.77-8.08). In the multivariable analysis, the number of staff remained significantly associated with TB in healthcare workers (OR=3.33, 95%CI 1.37-8.08).

Conclusion

The high rate of TB in healthcare workers suggests a substantial nosocomial transmission risk, but the infection control audit tool which was used did not perform adequately as a measure of this risk. Infection control measures should be monitored by validated tools developed and tested locally. Different strategies, such as routine surveillance systems, could be used to evaluate the burden of TB in healthcare workers in order to calculate TB incidence, monitor trends and implement interventions to decrease occupational TB.     

Precocious development of hydatid cysts in a macropodid host

This study describes the pathological changes associated with an experimental infection of captive wallabies with Echinococcus granulosus. Adult and juvenile tammar wallabies (Macropus eugenii) were infected orally with 0, 1,000, 2,500 or 8,000 E. granulosus eggs. Lung cyst progression was monitored by chest radiography every 4 months until 16 months p.i. Animals were necropsied from 9 to 16 months after infection. Cysts were detected radiographically from 4 months onwards. The number of cysts per animal varied from one to 10 and the majority (36/40) of cysts established in the lungs. Infection rate was low (35.5%), but cyst development was more rapid and onset of fertility much earlier than has been recorded in sheep. Cyst growth resulted in loss of functional lung capacity, up to an estimated 28% within 14 months of infection. Degenerative changes in cysts were less common in tammars than has been reported in sheep, with gross degeneration of cysts identified in only two animals. Complications associated with lung cyst development included fatal anaphylaxis, pneumothorax and atelectasis. Seven of the 11 infected tammars died or were euthanased as a result of infection during the experiment. From the parasite's perspective, infection of this host allows a shortened life cycle and correspondingly greater biotic potential. We believe this is the first published study that demonstrates the susceptibility of tammar wallabies to hydatid disease and confirms their suitability as a laboratory model for studying the disease in macropodids.     

Descriptive epidemiology of Kaposi sarcoma in Europe. Report from the RARECARE project

Kaposi sarcoma (KS) is a virus-related malignancy which most frequently arises in skin, though visceral sites can also be involved. Infection with Kaposi sarcoma herpes virus (KSHV or HHV-8) is required for development of KS. Nowadays, most cases worldwide occur in persons who are immunosuppressed, usually because of HIV infection or as a result of therapy to combat rejection of a transplanted organ, but classic Kaposi sarcoma is predominantly a disease of the elderly without apparent immunosuppression. We analyzed 2667 KS incident cases diagnosed during 1995–2002 and registered by 75 population-based European cancer registries contributing to the RARECARE project. Total crude and age-standardized incidence rate was 0.3 per 100,000 per year with an estimated 1642 new cases per year in the EU27 countries. Age-standardized incidence rate was 0.8 per 100,000 in Southern Europe but below 0.3 per 100,000 in all other regions. The elevated rate in southern Europe was attributable to a combination of classic Kaposi sarcoma in some Mediterranean countries and the relatively high incidence of AIDS in several countries. Five-year relative survival for 2000–2002 by the period method was 75%. More than 10,000 persons were estimated to be alive in Europe at the beginning of 2008 with a past diagnosis of KS. The aetiological link with suppressed immunity means that many people alive following diagnosis of KS suffer comorbidity from a pre-existing condition. While KS is a rare cancer, it has a relatively good prognosis and so the number of people affected by it is quite large. Thus it provides a notable example of the importance of networking in diagnosis, therapy and research for rare cancers.     

Incidence of trauma in a breeding and rearing colony of cynomolgus monkeys (Macaca fascicularis)

A statistical survey was performed in 1982 to ascertain the incidence of various diseases, especially trauma, in the cynomolgus monkey colony at Tsukuba Primate Center for Medical Science. In total, 1,029 cases of disease, occurred of which 866, 89 and 74 were surgical, internals and reproductive disease cases, respectively (Table 1). Among the 866 surgical cases, trauma (746 cases) was most often observed (Table 2). It was shown that trauma occurred most frequently during the group feeding of juvenile monkeys (Table 3). Analysis of the factors influencing the incidence of trauma during group feeding was carried out. As a result, it was revealed that the number of days after beginning group feeding and the age at which group feeding was begun had marked influences on the incidence of trauma (Figs. 1 and 2). However, there was no significant relationship between the incidence of trauma and the number of animals per group or the sex-ratio in a group (Tables 4 and 5). From the present survey results, a prospective rearing system should be established to reduce the incidence of trauma in the cynomolgus breeding and rearing colony.     

Distribution of surgical hydatidosis in Tunisia, results of 2001-2005 study and trends between 1977 and 2005

We have performed an exhaustive retrospective study in all surgical wards (54 services in 35 hospitals) which usually carry out surgical treatment of hydatic cysts in the country, covering the period between January 2001 and December 2005, in order to determine the annual surgical incidence of human cystic hydatidosis in Tunisia. A total of 6249 surgical interventions were recorded during the period 2001-2005. The highest proportion was recorded in the hospitals of Tunis District (42.9%). The service of thoracic surgery from Ariana hospital occupies the first rank (95%). The yearly incidence rate varies between 11 and 13.6 per 100,000. Calculated over the 5 years period, the incidence rate is 63.2 per 100,000 inhabitants, which means an average yearly incidence rate of 12.6 per 100,000 [12.28-12.99]. Governorates of the North West and the Western Central regions of the country are the most endemic area with an average annual incidence rates varying between 19.2 and 33.9 per 100,000, which is at least once and half higher than the national level. After 30 years (1977-2005), the average annual incidence rate slightly dropped, from 15 to 12.6 per 100,000, proving that such zoonosis remains a problem of public health in Tunisia. In order, to control in more or less short term this heavy burden disease and public health expenditure, the only efficient way is the prevention of the diseases with a mass treatment campaign of dogs, principal host of the parasite.     

Hand infections in dental personnel

In an attempt to study the incidence of hand infections in dental personnel, a standardized survey was submitted to 715 dental professionals and hygienists throughout the state of Nebraska. Of those surveyed, 508 responded (71 percent). Ninety-eight of the 508 respondents reported an infection (19.29 percent). The rate of infection was found to correlate positively with the number of patients seen per week. The rate of infection was increased in respondents with chronic disease (e.g., diabetes mellitus) versus those without chronic disease (33.33 vs. 18.59 percent). In the dental professionals surveyed, it was found that the rate of infection in those who did not routinely wear surgical gloves was significantly greater than in those who did (28.6 vs. 17.6 percent). The morbidity of infections acquired in dental practice can be substantial. A percentage of individuals must leave their practice for surgical treatment. A number have acquired hepatitis B (although none in this study), and exposure to the HTLV-III is possible. We conclude that some protection from infection can be achieved with the routine use of surgical gloves, and this practice should be considered by all, particularly those with chronic disease.     

Prevalence and characterization of hydatidosis in Najdi sheep slaughtered in Riyadh city,Saudi Arabia

Hydatidosis is considered to be one of the important zoonotic diseases and has a significant public health importance due to the difficulties of the diagnosis. Domestic animals act as intermediate hosts and the main reservoir for the disease in humans. The main purpose of this work therefore was to determine the prevalence of hydatidosis in Najdi sheep slaughtered in Riyadh city, Saudi Arabia. Cyst location and cyst fertility and viability were also estimated, together with effect of seasons, age and sex on the prevalence of the infection. The prevalence of hydatidosis was evaluated by post-mortem examination, with intensive inspection of the visceral organs of 2785 Najdi sheep. The infection was found to prevail throughout the year in both sex, with an overall prevalence of 2.33%. The highest prevalence was recorded in winter (6.48%) while the lowest was encountered in summer (1.36%). Females were proved to be more prone to infection (70.7%) than males (29.3%). In the present study, younger sheep tended to have a higher prevalence of infection than older ones. The most commonly infected organ was the liver, with a prevalence of 81.5%. The recorded cysts showed a fertility rate of 75.4%, and a high viability rate of 61.2%. Hepatic cysts were the most fertile and viable ones (46%), while calcified cysts were not recorded during the study. Measurements of recorded cysts in all organs ranged from 2 to 6?cm in diameter.In conclusion, the high fertility and viability rate of the recorded cysts suggest that sheep are a potential source of hydatidosis transmission to dogs and the continuation of its life cycle in this region. Consequently, authorities are recommended to instigate stricter regulation of the slaughtering process, including the secure disposal of infected offal so as to minimise the transmission of cysts from slaughter houses, along with treatment of stray dogs.     

Ovarian cysts and their consequences on the reproductive performance of swine herds

The aim of this work was to determine the incidence of ovarian cysts in the breeding herd and their consequences in the reproductive performance of the herd. Data from 1990 cyclic sows from two farms, with 0-12 parities, lactation length between 6 and 47 days and weaning-estrus interval between 0 and 32 days were evaluated by ultrasound examination for cyst incidence. As cyst was considered an anaechoic structure with smooth and thin walls with a diameter larger than 2 cm that remained visible for at least 5 days after estrus onset. Cyst incidence was found to be 2.4%. Sows with ovarian cysts have a greater return to estrus rate (34.0 x 7.7%, P<0.01), and cysts were associated with around 10% of regular and irregular return to estrus patterns on both farms. The adjusted farrowing rate (52.2 x 90.0%, P<0.01) and anestrual sows that were not pregnant (10.6 x 0.6%, P<0.01) were also influenced by the appearance of ovarian cysts, but they did not influence litter size (P>0.05). The incidence of cysts was not influenced by parity (P>0.05). Sows with shorter lactation had a greater incidence of cysts (P<0.05). Sows with a weaning-estrus interval shorter than 3 days had a greater incidence of ovarian cysts (P<0.05). The time of the year had no influence on the incidence of ovarian cysts (P<0.05).     

Evidence for Finely-Regulated Asynchronous Growth of Toxoplasma gondii Cysts Based on Data-Driven Model Selection

Toxoplasma gondii establishes a chronic infection by forming cysts preferentially in the brain. This chronic infection is one of the most common parasitic infections in humans and can be reactivated to develop life-threatening toxoplasmic encephalitis in immunocompromised patients. Host-pathogen interactions during the chronic infection include growth of the cysts and their removal by both natural rupture and elimination by the immune system. Analyzing these interactions is important for understanding the pathogenesis of this common infection. We developed a differential equation framework of cyst growth and employed Akaike Information Criteria (AIC) to determine the growth and removal functions that best describe the distribution of cyst sizes measured from the brains of chronically infected mice. The AIC strongly support models in which T. gondii cysts grow at a constant rate such that the per capita growth rate of the parasite is inversely proportional to the number of parasites within a cyst, suggesting finely-regulated asynchronous replication of the parasites. Our analyses were also able to reject the models where cyst removal rate increases linearly or quadratically in association with increase in cyst size. The modeling and analysis framework may provide a useful tool for understanding the pathogenesis of infections with other cyst producing parasites.